One of the most aggressive of the ancient space going races is the K'N'Tara. A warlike race, the K'N'Tara are the source of the mythology of the "centaurs" on ancient Earth. Humanoid from the waist up, they have the body of a horse from the waist down, with two large ears on the sides of their head. Spots and striping are rare but not unheard of. K'N'Tarans are also extremely susceptible to alcohol, very evident with their love of drinking wines and ales.
Their biology is such that four out of five of their children are male. This creates a lot of infighting and duels between them, but also has allowed them to breed a stronger and more powerful race. To redirect this aggressiveness, the K'N'Tara Federation conquer planets. If the world has no resources or technology which they can use, they will wage a conventional war. However if the planet is strategically placed, or has resources or technology, they will launch a "War of Conversion".
In a war of conversion, the K'N'Tara will send down caches of transformational weaponry. When one of these pseudo-meteorites lands, it awaits for a receptive subject or subjects to get within range. It will then open, transforming all nearby into K'N'Tara females, each with a reprogramming to fit their new role, but also with the skills and knowledge from their former lives.
The K'N'Tara Federation has a rigid cast system, and once a planet is conquered, the changed are then given one of three classifications: Caretaker, Assistant, or Community Servant.
The Caretaker's role is akin to that of a "nanny", feeding and caring for K'N'Taran foals. They are given regular injections to keep their biology producing sustenance for the children.
Assistants are the "secretaries". In charge of running operations and other things that the males can't be bothered to do. Most are assigned to a single Male.
Community Servants take care of the upkeep of the community, buildings, roadways, etc.
There are two other "classifications". The first is used when the mare goes into heat. The nearest males fight for her attention, with the strongest mating with her. When she becomes pregnant, she is classified a "breeder" for that time, with no other duties except taking care of the unborn child.
The other is for the changed who either break their programming or are all together useless. K'N'Taran males use them to practice their hunting abilities. Rarely some of these K'N'Tara will manage to escape, and are sometimes picked up by the Resistance.
The Resistance is a growing group of the Changed who have broken their programming and are trying to stop the K'N'Tara from conquering more planets. Even though they are no longer under the rein of their masters they still find returning to their original forms impossible. Supplied by other races who also dislike the K'N'Tara the resistance is slowly becoming a real thorn in the hoof of the Federation.